Chapter 9: Methods of Separation in Everyday Life (Chemistry)

(ii) Sorting. Handpicking is used to pick out and sort a small number of larger, easily visible items (such as stones from rice or dal).

(ii) Sorting

(iii) Cream from milk. Churning milk or curd separates the lighter cream (butter) from the rest of the liquid.

(iii) Cream (butter) from milk

(iii) Pore size. The holes (pores) of the filter must be small enough to stop the solid particles but let the liquid pass through.

(iii) Pore size

(i) T. The Sun's heat evaporates the water and leaves the salt behind (this is how salt is made from sea water).

(ii) T. Handpicking is practical only when the unwanted items are few and easy to see (e.g. a few stones in rice).

(iii) F. Threshing separates grains from stalks. Puffed rice and rice grains can be separated by sieving (or winnowing, since puffed rice is light).

(iv) T. Oil does not mix with lemon water and floats on top, so the oil layer can be poured off carefully (decantation).

(v) F. Rice flour does not dissolve and its fine particles pass through a sieve. It is separated from water by sedimentation and decantation, or by filtration.

(i) T (ii) T (iii) F: use sieving or winnowing (iv) T (v) F: use sedimentation and decantation, or filtration.

(i) – (d), (ii) – (e), (iii) – (a), (iv) – (b), (v) – (c)

Decantation is used when the solid is heavy and insoluble and settles down quickly at the bottom, leaving clear liquid above, for example sand or stones in water, or washing rice and dal (the water is poured off). It is also used to separate two liquids that do not mix, like oil and water. It is quicker and needs no filter paper. Filtration is needed when the solid particles are very fine and do not settle (like chalk powder in water).

When the insoluble solid is heavy and settles quickly (sand in water, washing rice or dal), or for liquids that don't mix like oil and water.

Yes, filtration. The hair inside our nose acts like a filter: it traps dust, pollen and other particles from the air we breathe in, and lets clean air pass into the body.

Nasal hair works like a filter, trapping dust and particles and letting cleaner air pass through.

Masks are generally made of cloth (cotton) or layers of non-woven polypropylene fabric (as in surgical masks and N95 masks). They work as filters: their tiny pores stop dust particles, germs and droplets carrying the virus from being breathed in or spread to others, while air can pass through.

Cotton cloth or layered non-woven (polypropylene) fabric; they filter out droplets, germs and dust while letting air pass.

1. Handpicking: pick out the potatoes, as they are big and easy to see.
2. Dissolving: put the remaining salt and sawdust in water and stir; the salt dissolves, the sawdust does not.
3. Filtration: filter the mixture; the sawdust stays on the filter paper (dry it in the Sun), and the salt solution passes through.
4. Evaporation: heat the salt solution (or keep it in the Sun); the water evaporates and the salt is left behind.

(Sawdust can also be skimmed off the top of the water before filtering, since it floats.)

Handpick the potatoes; dissolve the rest in water; filter out the sawdust; evaporate the water to get the salt.

Leela was working in the farm with her father when she realised that they left their drinking water at home. Before her father felt thirsty, she went to the nearby pond to fetch some water. After obtaining some water in the container, she noticed that the water was muddy and unfit for drinking. To purify the water, she kept it for some time and then she filtered the muddy water using a piece of muslin cloth. Leela, then, boiled the water for about 10 minutes in a covered pan. After cooling, she filtered it again and made it fit for drinking. She served this water to her father while having food, who blessed her and appreciated her efforts.

Title: "Leela Makes the Pond Water Safe" (or "Clean Water for Father").

thirsty, water, unfit, filtered, muslin cloth, boiled, cooling, filtered, fit. Title: e.g. "Leela Makes the Pond Water Safe".